CHRIS STEVENSON, QMI Agency

As I’ve said before, after researching a series on concussions and talking to experts in the field, there really is no such thing.

Wasn’t the condition of Pittsburgh Penguins captain Sidney Crosby, who hadn’t been diagnosed with a concussion previously, described as a “mild” concussion in early January?

We know how that turned out.

Now that is the description being given to the brain trauma suffered by Boston Bruins centre Patrice Bergeron Friday night when he was hit by Philadelphia Flyers forward Claude Giroux.

The good news is the injury suffered by Bergeron did not seem to be as severe as the other two diagnosed concussions he has suffered in his career. But mild? When it comes to the brain, as Crosby and others have shown us, that’s a slippery slope.

Bergeron was taken to the “quiet room,” under the NHL’s new concussion diagnosis protocol and given a modified SCAT-II test which he apparently failed.

“(He) was deemed unable to return, but what I’m told is that the concussion is mild,” said Bruins general manager Peter Chiarelli, who talked with Bergeron after the Bruins swept the Flyers in the Eastern Conference semifinal.

With the rest of the Bruins having Saturday off, Chiarelli met with the media at the club’s practice facility.

“I have not heard about him today. I think he was still sleeping this morning, so that’s where that stands.

“When I spoke with him after the game he was a little despondent, but he was quite lucid to me. He was despondent having suffered another concussion.”

Chiarelli said he took the issue of the hit - which he thought was a “shade” late - up with the league, but didn’t expect anything to come of it.

So now Chiarelli - in his daily brainstorms with coach Claude Julien - must consider the options without Bergeron, who will likely miss at least the first two games of the Eastern Conference final against the Tampa Bay Lightning (considering a player must be symptom-free for a week, generally speaking, before being allowed to return to the ice). Bergeron was second in playoff scoring and was winning faceoffs at a 64% clip.

Rookie Tyler Seguin, the second pick overall in last summer’s draft (thank you, Kessel), will go into the lineup, but just where and with whom remains to be seen.

It is likely Chris Kelly, acquired at the trade deadline from the Ottawa Senators, will be elevated from the third to the second line to take Bergeron’s place between Mark Recchi and Brad Marchand. He took a few shifts there in the Bruins clinching 5-1 win Friday after Bergeron exited early in the third.

“Kelly is a good two-way player. He makes strong plays and we’ve seen him on that other line and his style of play is not unlike Bergy’s,” said Chiarelli. “Watching him (Friday) night it looks like it would be a good fit.”

That might leave Seguin to take Kelly’s place on wing or centre (Kelly played both) with Rich Peverley and Michael Ryder.

This could be the first real test the Bruins face in terms of injury. So far, they have missed top defenceman Zdeno Chara for one game, as he could not play in Game 2 of the opening series against Montreal because of dehydration.

If anything has marked the Bruins in these playoffs, much like the Lightning, it’s been production from up and down the roster. When the Habs shut down the top line of David Krejci, Milan Lucic and Nathan Horton, Kelly’s line delivered.

The Krejci line was dominant against the Flyers with Lucic scoring his first two goals of the post-season Friday night.

“We have an injury now,” said Chiarelli, “so we’ll see how our depth gets tested.”